Here is a closeup of the pinhole (I took this picture when I first got it, before I even cleaned it). It had a broken-off pin up inside it, unscrewing it I could see that it was oversize, and well made... clearly different than a standard pin.

I have wondered about these for years, and hypothesized about their intended use, but nothing has ever come to my attention that would really prove anything. I was talking about this with another long-time collector from California, and he indicated that he had found an old pole with a strange side bracket years ago on an EC&M line that he always wondered about... perhaps it would fit a CD 140.5? Arrangements were made for a test fitting, and at a later date I made a trip over to his house... [id=348775443]